DC-to-DC converters are well known. A DC-to-DC converter is a device that receives a DC input voltage and produces a DC output voltage. The output voltage is typically produced at a different voltage level from the input voltage. DC-to-DC converters can produce high voltage usable for low power applications including supplying power to mobile devices such as cellular phones and laptop computers.
Sensing supply current is one task that a DC-to-DC converter performs during a voltage conversion process. Supply current sensing in a DC-to-DC converter is generally implemented by sensing the voltage generated by the supply current flowing through a sense resistor. Sometimes the voltage across a switch is directly sensed where the “on” resistance of the switch is used as a sense resistor. Because the sense voltage is based on the supply current, the behavior of the supply current (e.g., glitches) will be reflected in the behavior of the sense voltage. This is problematic, because the resulting sense voltage may be very noisy (i.e., having a high ripple). As a result, current sensing of the conventional DC-to-DC converter is performed with poor accuracy.
Accordingly, what is needed is an improved system for sensing the supply current of a switched DC-to-DC converter. The present invention addresses such a need.